This invention relates to links which are releasable in response to predetermined increases in temperature, and more particularly to releasable links for use with devices such as fire/smoke dampers in air ducts, plenums, chambers and the like.
Fire dampers, smoke dampers, air control dampers or other fire protection equipment which may be located in ducts, plenums, chambers and the like are often preferably installed with activation devices which will respond to increases in temperature within the duct, etc., within which the damper or other fire protection apparatus is installed. In order to insure operation of such activation devices, however, it is advantageous to provide a mechanical-type of releasing device which may respond to a fail/-safe manner to such increases in temperature. Commonly, these devices have included fusable links which are disposed along cables located within the area to be sensed which will melt thereby releasing the cable and/or associated equipment in response to increases in heat. Alternatively, bimetallic releasing devices, such as those disclosed in my prior U.S. Pat. Nos. 3,889,314 and 3,725,972, have been utilized in such installations.
While the above devices have often provided satisfactory results, mounting them within a duct, plenum, or other chamber has often necessitated provision of an access door through the wall of the duct or plenum, so that they may be manually replaced or reset, as needed. Not only are such access doors relatively expensive, resetting or replacement of links disposed within the duct or plenum serviced thereby is often cumbersome, thereby tending to inhibit frequent testing of those devices even when those devices can be remotely activated, as by receipt of an electric or pneumatic signal. Additionally, cable mounting of such devices within a duct, plenum, chamber, etc., even if provided with remote activation capabilities, have not uniformly been readily testable by a safety engineer present outside the duct in the immediate vicinity of the damper for the purpose of evaluating the effectiveness of that activation.